Question about the Johnson temp control

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tigerface

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I use my chest freezer to chill my brew. Problem is though the freezer warms right up to 38 degrees before it starts to blow cold air again. And I set it up at 32-34 f. Is my unit toast? Do I need a new one? Any help would be appreciated. :(
 
I think you might have your differential set at 4 or 5. If that's the case, try setting it at maybe 2.
 
Thanks for replies everybody. I have it set up at 34-36 degrees. Pictured below is the control itself. I usually use chest freezer.
tempcontroller1.jpg
 
I have the digital controller so I'm not familiar with what you have. It looks like that controller has a 4 degree differential which you cannot change, so a setting of 34 should mean that the freezer will kick on at 34 and cool to 30. How quickly the air goes back to 34 is based on your freezer and the outside temp, etc. It sounds like the temperature dial on those things can be a bit suspect based on some reviews, so the controller set to 34 may actually be 38, but it also sounds like the error should be consistent. Remember than the temperature of your beer doesn't swing as largely as your air temp.
 
You get a direct temp output and you have more control, but it's not necessarily better for all applications. The air temp swing isn't a problem whether used for serving or lagering. I would be concerned with burning out your compressor if it is going on and off constantly. I don't know what you mean when you say it warms right back up to 38. Minutes? Hours? You need to monitor your chest freezer with a trusted thermometer
 
I am using a floor freezer. Normally used for food. But when I make a batch of beer I use it to cool my beer. The Johnson temp control has a probe which I let dangle inside. Yes of course when it cools to my desired temp it shuts off and when temp rises, freezer starts up again. I just checked it right now and it went up to 40f.
 
fold a few paper towels up and tape that over your probe to the side of your fermenter (carboy?)

What they meant above was that if your freezer is turning on and off a lot it's not good for it and the compressor life span will suffer.

If it cools to your set temp and then raises four degrees above before the freezer turns back on it's working how it should if that controller has a differential of four degrees. I didn't look it up so I'm just assuming its four degrees above the set point.

The main thing is you don't want your freezer turning on and off every five minutes.
 
I guess my concern or question was if there was something wrong with my temp controller. It never stayed exactly where I wanted it to stay. Which is exactly 35f. But I guess that's being too unreasonable. To ask it to keep temp of beer exactly where I wanted it the to be.
 
The A419 johnson controller will allow you to keep the liquid within a degree or so pretty easily. When doing that though the air temp will probably swing 4 or more degrees. Have you measured the temp of your beer at all or just the air?
 
And to explain further, the reason you can keep the temp tighter with A419 is because you can set the differential to be as low as 1, where I believe yours is unchangeable at 4. However, you do not want to keep the air in your chamber within one degree because the air changes temp more quickly than the beer, and you will unnecessarily overwork your chest freezer to an early death
 
I duct taped a piece of 4" x 12" x 1/2" foam to my fermentation bucket. Tape it on three sides and leave the top open. It acts as a holster for the probe to slip into. It keeps the probe pressed up against the vessel and insulates it from the air a bit.
 

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